In the biotech industry, companies mix various liquid, liquid/solid materials together such as cell culture media, buffers, reagents and other such materials as well as protein containing solutions. Typically this has been done in a steel vat or tank with the amounts of materials such as powder and liquid added in controlled amounts. A mixer such as a magnetically driven stainless steel mixer such as the Novaseptic® mixer from Millipore or a shaft driven mixer such as Lightnin® mixers available from SPX Corporation can be used. Additional supplements in liquid or powder form can also be added in the same mixing or in a subsequent mixing step(s). Once the solution is prepared it is filtered and may be used directly or sealed in sterile containers for future use.
To be safe, the solutions must be pure and sterile. Therefore, the equipment must be thoroughly cleaned such as with a sodium hydroxide (generally 1 M) solution and sterilized with steam between uses to ensure that no cross over material from the last mixing batch and no bacteria, mold or fungus from the environment is in the tank before a new batch is mixed. This cleaning and sterilizing process is labor intensive, time consuming, costly and often requires the partial disassembly of one or more components of the system and their reassembly afterward
An alternative has been to use a closed, presterilized plastic mixing bag and disposable mixing component such as is described in U.S. Pat. No. 7,278,780. However, it has issues with creating a vortex during mixing unless operated at slow speeds. Either alternative is undesirable. A vortex leads to inefficient mixing and therefore requires a large amount of additional time to ensure that the mixing is complete. In addition with protein containing streams, the vortex entrains air which has adverse effects on the proteins including oxidation and shear as will be explained below. The alternative, to mix at a speed below the vortex creation is also unacceptable as it too requires additional time and may never achieve suitable mixing results.
U.S. Pat. No. 7,547,135 suggests adding rigid baffles vertically along the interior wall of a rigid molded plastic container to reduce vortex formation and increase mixing efficiency. However, the handling and shipment of a large molded structure (up to 1000 or 2000 liters capacity) is inefficient as is the storage of such containers.
While it is desired to add rigid baffles to the sides of the container this has proven to be difficult. The baffles can adversely affect the ability to fold the bag for compact shipping. Additionally, they can rupture the bag when and where they the bag surface during transportation and shipping.
What is needed is a disposable container for mixing that has the advantages of the bag with the baffle/vortex inhibiting effect of the rigid baffles to enable simple and efficient mixing.